The climate envelope is the exterior shell of the building i.e. walls, floor and roof. Windows and exterior doors are also included in the climate envelope. Heat dissipates through windows and doors, walls, roof, floor and basement as well as through ventilation. Buildings should be designed such that energy consumption is reduced through low loss of heat, low need for cooling, efficient use of heating and cooling as well as reduced CO2 emissions. The recommended thickness of insulation in cold climates for both new buildings and retrofit insulation is 30-50 cm for walls, 40-50 cm for roofs, and minimum of 30 cm for floors (according to the Swedish Energy Agency). There are several disadvantages to this.
A considerable increased thickness of insulation inside reduces the living space up to 10%, alternatively the cost per square meter with retrofit or original exterior insulation will increase. Thermal bridges, a poorly insulated envelope, are usually due to leaking window trim, doors, spaces between stories, eaves of the roof, and exterior corners of the climate envelope. Thermal bridges causes heat losses and cold surfaces indoors. The insulating capacity of wood is 8 times that of a concrete beam which is 6 times heavier. One cubic meter of wood reduces CO2 emissions about 1.1 tons and stores 0.9 ton (Mitthögskolan, Gustavsson). Cement and concrete account for 4-5% of total global CO2 emissions. Houses built of solid wood with a very long life span are built on a small scale. A well insulated energy efficient climate envelope with solar thermal collectors and panels is a climate positive climate envelope.
Construction technique for sealing houses is costly. The risk for damp damage increases if walls are thicker than 20 cm. A thicker, harder exterior shell is often avoided to reduce the risk for damp penetration (IVA, seminarium Trähusbyggande, 2009, professor KTH). Thin insulation, e.g. 3 cm insulation, exists, which corresponds to 21 cm mineral wool insulation according to independent testing institute. Traditional methods using bulky insulation are most common. Sealed houses require good ventilation and heat exchangers which recycle heat from exhaust air. Ventilation, air conditioning and heating systems available on the market for residential houses, apartments, commercial spaces and buildings are complex and most fresh air intake and air conditioning occurs from above. Hot water is stored at high temperatures, with high cost of energy as a consequence. Solar panels and collectors are developed for use during the warm part of the year, pointing south, east and west and during the sunniest period, and there is a risk of producing an excess of heat energy which in turn requires a need for heat storage e.g. extra accumulator tanks for hot water. Often the indoor temperature is too high. During the cold season too little heat is produced since solar panels, solar collectors, are too small. In hot climates, in warm countries, energy is spent on cooling.
Energy spent on ventilation can be reduced by half compared to fresh air intake from above. Computer simulations of air movements around heat sources in a room shows that heat rises naturally towards the ceiling. Cool fresh air from intake below automatically find its way to heat sources, where heat exchange occurs. Research shows how fresh air intake should be managed in order not to disturb the natural heat diffusion from heat sources in the room. Heat exchange can be concentrated to the heat sources in the room in such a way that it is not experienced by a human being as a draft of air. The need for energy can be reduced by half compared to fresh air intake from above. This significant potential to reduce energy consumption has been verified through studies in real buildings (Cho, Awbi, Karimipanah, Blomqvist, Sandberg, Moshfeg) Traditional building methods with cooling elements in the ceiling and fresh air intake from above means increased use of energy and poorer indoor air quality since warm rising impure air mixes with descending cool air, which puts demands on air circulation.
PCM (Phase Change Materials) is a well known technology (Sundberg, Termisk energilagring genom Fasändringsprocesser. Luleå tekniska universitet. Avdelningen för Förnyelsebar energi, 2005.) The process for PCM-technology can be described in two steps. In the first step heat is transferred to the PCM from a surrounding heat source. This happens when the temperature of the heat source is higher than the temperature of the PCM. The heat can for example consist of the heat from a human body or the indoor air heated by the sun. In this step, the PCM acts as a heat reservoir, absorbing the heat and changing phase, e.g. from solid to liquid.
The process implies that the thermal energy of the PCM increases while the opposite goes for the heat source, where the thermal energy drops. In this step something in the vicinity of the PCM is cooled, e.g. the warm human body or the indoor air by the PCM when it goes through its phase change. At the same time, the PCM is charged with heat, heat which is now latent, and is ready to be released. The heat is released from the PCM to a surrounding heat reservoir in the second step, when the temperature of the PCM is higher than the temperature of the heat reservoir.
The heat reservoir may, in this step, be the original heat source which has cooled and/or another receiver in the vicinity of the PCM. The PCM may, in this step, be seen as a heat source and diffuses the stored heat when the temperature of the PCM drops and the PCM goes through a change of phase in the opposite direction, e.g. from liquid to solid. The process implies that the thermal energy of the PCM drops while the opposite is true of the heat reservoir, where the thermal energy increases.
In this step the PCM transfers heat to something in its surrounding, e.g. a chilled human body or cold indoor air, at the same time as the PCM starts cold storage. The PCM has now acquired the ability to absorb heat, if the temperature of something in its surrounding rises, and can in that way again cool something in its surrounding in accordance with step one. The PCM is selected on the basis of the phase change temperature depending on the purpose of the system or product and application.
If the PCM, for example, is designed to provide cooling to people in a home, a phase change temperature below 20 degrees centigrade can be suitable, and if instead it is used for cooling groceries another phase change temperature may be suitable. The amount of PCM used is different depending on the heating and/or cooling capacity it has to meet. The amount of PCM used, corresponding to a certain heating and/or cooling capacity, doesn't necessarily have to consist of a single unit but can be divided into sub-units. There are advantages to splitting the PCM into small units to improve the heat transfer to and from the PCM and the space available for the PCM to be of different sizes.
At the end of the 19th century, PCM that melted/turned solid at 44.4 degrees centigrade was placed in metal cases to store heat in train compartments and in the beginning of the 20th century PCM was used to store cold in different train transport applications (Dinçer. och Rosen, 2002). Later, hot plates were developed to enable hotels and restaurants to keep the food hot for the guests and bed warmers to keep patients in hospitals comfortable (Lane, 1983). In the beginning of the 1940-ies PCM for bed warmers (Bowen, 1949) were developed. In 1946 PCM was used in a house to store the energy from a number of solar collectors using a fan system. By using 21 tons of PCM the system could store around 11 MJ of heat (energy).
The LTES-system had the capacity to supply 21 degree heat to the house during periods of up to seven days with cloudy weather, without having to use any other system for heating (Frysinger och Sliwkowski, 1987). A system solution for buildings was patented during the 1960-ies by Telkes, together with Herrick and Etherington at General Electric and was later used in the USA (Bromley och McKay, 1994).
Dow Chemical, with a leading research unit of PCM during the 1970-ies, performed a study, commissioned by the National Science Federation in the USA, of the potential of nearly 20 000 different PCMs. The outcome was that only about one percent of all the investigated PCMs were considered as having the potential for practical applications meriting further studies. These PCM were different congruent melting salt hydrates and organic material (Lane 1983).
During the 1970-ies and 1980-ies several organizations could supply phase change products for solar heat storage. Dow Chemicals had a product which melted/turned solid är 27.2° C. but the product got no traction on the solar heating market. In 1982, Transphase Systems Inc. installed a cold-storage system for commercial and industrial buildings which used PCM salts (Dinçer och Rosen, 2002). PCM technology is used for long and short term storage of heat and cold.
In long term storage the object is to minimize the heat transfer between the PCM and its surrounding, since even a small heat transfer can amount to great losses over a storage cycle. In long term storage it is important to insulate the PCM. Long term storage in this context means months. In short term storage the time span is hours and days. In short term storage the PCM must give off/absorb heat energy quickly and in that way respond more directly to changes in temperature.
Inside buildings, the atmosphere is perceived as comfortable if the temperature varies very little over 24 hours and PCM can be used to give a constant indoor temperature in the building since it is suitable for cooling, and customarily cold is supplied to a room from the ceiling level. PCM can also be integrated into building components—ceilings, walls, floors—or placed as separate units, or in furniture, in order to minimize temperature fluctuations indoors; when the indoor temperature is high the PCM absorbs the heat, and releases it when the temperature drops.
Buildings can thus be erected in a new way; either with active heating/cooling systems, which have lower capacity and/or with smaller massive building components—through their comparatively high intrinsic storage capacity massive building components provide a “slower” more gradual shift of temperature between day and night. PCM is used in floor components (Rubitherm, 2005) and wall components (BASF, 2005).
PCM technology can be integrated with other already existing energy systems, primarily in order to manage the peak load in the energy system, and one application is thermal systems which use PCM to store solar heat. PCM systems are considered feasible in ventilation systems and hot water tank (accumulator tanks) in buildings. There are several demo sites where PCM technology is used in this way. Belusko and Saman at the University of South Australia have developed a solar heat system which uses corrugated iron as a solar collector to heat air. The hot air is then circulated through a distribution system indoors. PCM is connected to the distribution system and is used for heat and cold storage.
The company TEAP has demonstrated a hot water system which uses PCM. The system is dimensioned for detached residential houses. The system used an inorganic salt with a melting point of 58° C. 150 kg PCM was placed in a plastic container before installation inside a 250 l hot water tank. The PCM absorbs heat from a 2.4 kW electric heater until the desired temperature is reached.
When heat is needed cold water is allowed to flow through the water tank before it is conducted to the end user. A test of Standard has been performed by National Association of Testing Authorities of Australia. The test implies that hot water is drawn on several consecutive occasions until the temperature has dropped from the original 75° C. to 45° C. The tests showed that with PCM in the hot water tank, 408.6 l of hot water could be obtained before the temperature of the water had dropped to 45° C. Without PCM, only 230 l of hot water could be drawn. A system such as this can be charged with heat from a solar collector.
Examples of PCM systems which supply heat and cold where needed are relatively few today. It is easy to see advantages to using PCM technology. If PCM technology is used, part of the peak load of a randomly chosen energy system can be supplied. This should mean lower capital expenditure since an energy system dimensioned for a lower peak load can manage with components with lower capacity. For example, smaller cooling systems, pumps, fans etc. Since PCM technology enables storage of heat for later use, the use of the technology will stimulate renewable energy sources, e.g. solar heat.
This is because these energy sources often supply energy when the need for energy is low and by using PCM technology the conditions allow increased use of renewable energy sources, at the expense of fossil energy sources. Today, primarily solid-liquid PCM is used. It has relatively good energy storing capacity, relatively small changes in volume during phase changes, and has phase change temperatures ranges which can be used to keep us human beings comfortable.
WO 85/00212 shows a solar collector system specially developed for direct heating of a house using heat storage from PCM. A PCM changes phase at a certain temperature and thermal energy is stored or transferred, giving heat and/or cold according to the needs. DE102006020535 (A1) concerns a solar system with PCM and a heat pump for heating and cooling. A PCM device is described in WO 85/00212. U.S. Pat. No. 4,908,166 refers to construction materials and PCM. PCM products with different characteristics for buildings can be bought from, for example, BASF and DuPont. U.S. Pat. No. 4,924,935 describes a flat roof/ceiling system where PCM material is used. WO2006128565 is a patent for PCM material. SE08023A-1 concerns a cooling and heating system for buildings based on thermal energy, where a liquid tank is part of walls, ceilings and floors.
It is known that an insulated space under the ground floor in a building can be used for heating, as described in WO2008105733 (A1) US2008164333 (A1), WO2008105733 (A1). There are PCM patents regarding air conditioning in ceilings DE102006029597 (A1). SE-B-468057 SE514680C2 describes a floor system for heating and cooling. Solar collectors for heating air for ventilation, water and/or as a medium to transfer heat to a heat exchanger is known. FR 2500036 is a simple air solar collector. U.S. Pat. No. 4,054,124 and U.S. Pat. No. 4,262,657 show a more sophisticated solar collector. One common trait is that the back plane of the solar collector panels are insulated to improve the thermal effectiveness of the collector. GB 2 214 710 shows a combination of a solar collector and solar panel for heating. DK 174935 BI has solar collectors and solar cells with a rear side which allows air to pass through.
None of the above patents solve the problem with a climate envelope in its entirety exemplified with environmentally friendly wood technology, thin effective heat storing insulation, PCM, ventilation with fresh air intake from below, minimization of thermal bridges, cost effective solar heating, heat storage and water heating at lower temperature, air cooling, and furthermore, offers a complete cost effective climate positive climate envelope which is easy to assemble.
The majority of climate envelopes for residential buildings are built at the building site with different craftsmen/trades represented or, alternatively, supplied in modules to reduce the time for construction. A technique where a normal buyer can assemble/erect most of the house by him- or herself like furniture, is lacking. Bought as flat packages to be assembled by the buyer. The invention also includes methods to produce climate envelopes for housing with a 15 square meter footprint and up to 3 meters in height, which can be assembled into larger buildings and which are mobile.
In traditional houses there are functional solutions inside to the climate envelope for heating, sleeping, sitting and eating. Technology for keeping groceries refrigerated is known. The disadvantage is that energy is consumed even when the outside temperature is low. In the past, larders with simple cooling/ventilation were standard. Techniques to collapse beds, couches and tables and store groceries at low temperature, heat food in a small area and purify and collect rain water and store water are well known envelope technique applied to caravans, boats and leisure- and hotel buildings. Space in the outer layer of the climate envelope can be used to heat and cool beds, furniture, food and boil water. To integrate parts of this function with the climate envelope can result in better heat efficiency.
Heating and cooling of buildings is the main cause of global greenhouse gas emissions. The use of well insulated, ventilated climate envelopes and renewable energy can reduce emissions. It is difficult to climate insulate, ventilate, store and distribute solar energy efficiently in a building. None of today's traditional climate envelope solutions combine thin effective insulation with PCM to store heat from the sun, and heat and cold from water and air. Climate positive climate envelope material according to the present invention is a thin ventilated thermos-like shell of wood which stores heat from, for example, the sun and cold storage from, for example, the air with good housing function and easy to install. All of the above is based on the present invention.